Question about 1991 Cadillac DeVille

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Rough idle after warm up

My 1991 cadillac devile(4.9) runs great when cold,but after it warms up it starts to run rough. No engine lights come on dash indicating a problem. I have also changed the air and fuel filter. the car has 102k. miles.

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  • Anonymous Mar 18, 2014

    My car is a 2005 Altima with 168000 miles. No problems in past.

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  • Cadillac Master
  • 6,982 Answers

I'd take a look at the temp sender...the engines computer may be "thinking" the engine is still cold when it's not. That would cause it run rich (and rough) after it's warmed up. Generally the sender can be tested with an ordinary volt/ohmeter but you will need the specifications available in most inexpensive manuals. As with any complicated electronics system, I can only give you my best guess, without the luxury of doing any hands-on testing myself.
Good Luck!!

Posted on May 28, 2009

  • Richard Scordino May 28, 2009

    I'd take a look at the temp sender...the engines computer may be "thinking" the engine is still cold when it's not. That would cause it run rich (and rough) after it's warmed up. Generally the sender can be tested with an ordinary volt/ohmeter but you will need the specifications available in most inexpensive manuals. As with any complicated electronics system, I can only give you my best guess, without the luxury of doing any hands-on testing myself.
    Good Luck!!

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